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Office Message Encryption - Recipient not able to open office attachments

GonWild 426 Reputation points
2020-09-15T13:31:31.05+00:00

Hello,
I'm testing the implementation of OME in our organization, and I have a question:

Sending a word/excel attachment in an encrypted email to a recipient with no Microsoft 365 subscription, results in recipient not able to open the file. The preview function in the browser for viewing the encrypted message is able to view the file, but downloading and trying to open/edit the file fails. Opening a excel file in XLS viewer or older local office version triggers RMS saying he doesn't have persmission to the document.

Is this by design, or am I doing something wrong? What are the requirements for sending OME encrypted office-file attachments to external recipients?

Microsoft 365 and Office | Office Online Server
Exchange | Exchange Server | Management
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  1. Vasil Michev 119.8K Reputation points MVP Volunteer Moderator
    2020-09-15T13:53:53.117+00:00

    This is by design, as protection is embedded in the file itself. If you want them to be able to download attachments in unencrypted form, use the configuration detailed here: https://techcommunity.microsoft.com/t5/microsoft-security-and/admin-control-for-attachments-now-available-in-office-365/ba-p/204007

    2 people found this answer helpful.

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  1. Yuki Sun-MSFT 41,376 Reputation points Moderator
    2020-09-16T04:37:53.07+00:00

    Hi @GonWild ,

    As michev said, by default the attachments in an encrypted message remain protected when downloaded. To allow recipients to download Encrypt-only attachments without encryption, please refer to the article shared by michev: 

    Set-IRMConfiguration - DecryptAttachmentForEncryptOnly $true

    And here is another official link for your reference: To manage whether email attachments are decrypted on download from a web browser

    If an Answer is helpful, please click "Accept Answer" and upvote it.
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